Target analysis of the inactivation of biological activity by ionizing radiation was applied to several major problems including the microsomal glutathione s-transferase, mitochondrial ferrochelatase, and the acetyl- LDL receptor. Fundamental studies of radiation energy transfer was examined in the avidin-biotin system. Objective: 1) An understanding to the nature of active structures in vivo which are involved in biochemical processes, principally by means of the technique of inactivation by ionizing radiation. 2) Detailed knowledge of the molecular damage caused by ionizing radiation and of the mechanisms of the transfer of radiation energy throughout these structures. Methods: 1) General biochemical techniques including enzyme reactions, fluorescence, and gel electrophoresis. 2) Ionizing radiation, usually high energy electrons from a linear accelerator, to expose samples under carefully controlled conditions.